Some will suggest swapping your engine for an AU engine but the 3.9 bottom end will be OK if you rebuild it properly. Use an EF/EL head and rocker gear. Compared to the BTR, there are plenty of performance parts for a C4. As first gear on the BTRs is too tall, most go for a lower diff ratio which in turn alters the speedo. Then you need a speedo converter. I had problems with the one I used and ditched it and the 3.7 diff after a while.

With the diff, just get a 28 spline LSD and axles instead of trying to swap the entire rear axle assembly. The EF/EL trailing arms, hand brake, etc don't change over without some fiddling around.

GdayJust seeking a little advise.I have a EA with a 3.9. I'm about the purchase a turbo kit which comprises of:TO4 turbo, genuine Garratt .60/1.15 (600hp)external gate + screamertuned length polished stainless high mount manifoldI'm looking for a EF/EL 4L to swap over before putting the kit on.Am I right in thinking the 4L is the superior engine, or shall I stick with the 3.9 and convert to thermos?Next is the drive line. I have read of people saying the 4spd auto is a stronger box. Is this true?The car won't be my daily, so I don't want drive ability over strength/performance.Is the C4 worth a look? Will it bolt up to the motor?If I get a EF/EL I would look at swapping the diff over. Is this a bolt in job? Do the spring perches etc line up?Thanks in advance.

1) What RwKw are you expecting to produce?2) What Booste do you paln to run?3) How many km on your current engine?4) What is the condition of your current engine?

These are questions that need to be anwsered first before it can be said that an engine is OK for turboing.

GdayJust seeking a little advise.I have a EA with a 3.9. I'm about the purchase a turbo kit which comprises of:TO4 turbo, genuine Garratt .60/1.15 (600hp)external gate + screamertuned length polished stainless high mount manifoldI'm looking for a EF/EL 4L to swap over before putting the kit on.Am I right in thinking the 4L is the superior engine, or shall I stick with the 3.9 and convert to thermos?Next is the drive line. I have read of people saying the 4spd auto is a stronger box. Is this true?The car won't be my daily, so I don't want drive ability over strength/performance.Is the C4 worth a look? Will it bolt up to the motor?If I get a EF/EL I would look at swapping the diff over. Is this a bolt in job? Do the spring perches etc line up?Thanks in advance.

1) What RwKw are you expecting to produce?2) What Booste do you paln to run?3) How many km on your current engine?4) What is the condition of your current engine?

These are questions that need to be anwsered first before it can be said that an engine is OK for turboing.

1) What RwKw are you expecting to produce? <250kw first stage of the build, then around 350kw2) What Booste do you paln to run? 9psi then 20ish3) How many km on your current engine? Unknown. Was informed around 10-15k but the guy lied about a few little things, so can't take his word. 4) What is the condition of your current engine? It's very powerless, but that could be something else. Clean, no leaks.

GdayJust seeking a little advise.I have a EA with a 3.9. I'm about the purchase a turbo kit which comprises of:TO4 turbo, genuine Garratt .60/1.15 (600hp)external gate + screamertuned length polished stainless high mount manifoldI'm looking for a EF/EL 4L to swap over before putting the kit on.Am I right in thinking the 4L is the superior engine, or shall I stick with the 3.9 and convert to thermos?Next is the drive line. I have read of people saying the 4spd auto is a stronger box. Is this true?The car won't be my daily, so I don't want drive ability over strength/performance.Is the C4 worth a look? Will it bolt up to the motor?If I get a EF/EL I would look at swapping the diff over. Is this a bolt in job? Do the spring perches etc line up?Thanks in advance.

1) What RwKw are you expecting to produce?2) What Booste do you paln to run?3) How many km on your current engine?4) What is the condition of your current engine?

These are questions that need to be anwsered first before it can be said that an engine is OK for turboing.

1) What RwKw are you expecting to produce? <250kw first stage of the build, then around 350kw2) What Booste do you paln to run? 9psi then 20ish3) How many km on your current engine? Unknown. Was informed around 10-15k but the guy lied about a few little things, so can't take his word. 4) What is the condition of your current engine? It's very powerless, but that could be something else. Clean, no leaks.

1) 250RwKw is bordering on the safe limits for a "GOOD" early 4 litre. 350RwKw is not going to happen on a stock bottom end.2) Same applies as above. I know that nore than one person has bent rods at less than 20psi (18psi was the number used) 3) So are you saying that the motor has just been rebuilt?4) ?

If you want 350RwKw and 20lb of boost, then built a new motor, Use an AU block and crank, stronger, Spool rods and forge pistons. Get head ported and a cam to suit.

GdayJust seeking a little advise.I have a EA with a 3.9. I'm about the purchase a turbo kit which comprises of:TO4 turbo, genuine Garratt .60/1.15 (600hp)external gate + screamertuned length polished stainless high mount manifoldI'm looking for a EF/EL 4L to swap over before putting the kit on.Am I right in thinking the 4L is the superior engine, or shall I stick with the 3.9 and convert to thermos?Next is the drive line. I have read of people saying the 4spd auto is a stronger box. Is this true?The car won't be my daily, so I don't want drive ability over strength/performance.Is the C4 worth a look? Will it bolt up to the motor?If I get a EF/EL I would look at swapping the diff over. Is this a bolt in job? Do the spring perches etc line up?Thanks in advance.

1) What RwKw are you expecting to produce?2) What Booste do you paln to run?3) How many km on your current engine?4) What is the condition of your current engine?

These are questions that need to be anwsered first before it can be said that an engine is OK for turboing.

1) What RwKw are you expecting to produce? <250kw first stage of the build, then around 350kw2) What Booste do you paln to run? 9psi then 20ish3) How many km on your current engine? Unknown. Was informed around 10-15k but the guy lied about a few little things, so can't take his word. 4) What is the condition of your current engine? It's very powerless, but that could be something else. Clean, no leaks.

1) 250RwKw is bordering on the safe limits for a "GOOD" early 4 litre. 350RwKw is not going to happen on a stock bottom end.2) Same applies as above. I know that nore than one person has bent rods at less than 20psi (18psi was the number used) 3) So are you saying that the motor has just been rebuilt?4) ?

If you want 350RwKw and 20lb of boost, then built a new motor, Use an AU block and crank, stronger, Spool rods and forge pistons. Get head ported and a cam to suit. Larger fuel pump, injectors, ECU, Tune etc.... New Gearbox, if using BTR.. time to spend big cash. If using C4, you will need a new bellhousing as well as a custom Convertor. C4 is a 3 speed. still dollars. Brake upgrade.... on and on.

With the diff, just get a 28 spline LSD and axles instead of trying to swap the entire rear axle assembly. The EF/EL trailing arms, hand brake, etc don't change over without some fiddling around.

What series came with the 28 spline? I won't need an LSD as I will run a spool.

SWC wrote:

1) 250RwKw is bordering on the safe limits for a "GOOD" early 4 litre. 350RwKw is not going to happen on a stock bottom end.2) Same applies as above. I know that nore than one person has bent rods at less than 20psi (18psi was the number used) 3) So are you saying that the motor has just been rebuilt?4) ?

If you want 350RwKw and 20lb of boost, then built a new motor, Use an AU block and crank, stronger, Spool rods and forge pistons. Get head ported and a cam to suit. Larger fuel pump, injectors, ECU, Tune etc.... New Gearbox, if using BTR.. time to spend big cash. If using C4, you will need a new bellhousing as well as a custom Convertor. C4 is a 3 speed. still dollars. Brake upgrade.... on and on.

Oh and I forgot, open your wallet wide........

The car has a gem engine in it.

I will do a compression check, but it seems under powered.

The reason I want to do it in two stages is to get it turbo'd asap then save for stage two whilst driving it.I like the idea of the C4. Where would I source the bell housing? and who could do me a convertor?3spd is fine, it won't be daily driven and it's currently 3spd.

the 3.9 being 8.8:1 compression will take well to boost, should have no trouble holding 10-14 psi all day long providing the engine is still healthy and its tuned well...but with no other work to the engine i cant see it getting over 250rwkw..

as for the gearbox, the std 3 speed from the ea wont last 10 mins, the btr 4 speed auto can hold up ok with 250rwkw, again depending on the condition of the box..

if your going to abuse it, a built c4 will be needed at a cost of between $3000-5000..

the 3.9 being 8.8:1 compression will take well to boost, should have no trouble holding 10-14 psi all day long providing the engine is still healthy and its tuned well...but with no other work to the engine i cant see it getting over 250rwkw..

as for the gearbox, the std 3 speed from the ea wont last 10 mins, the btr 4 speed auto can hold up ok with 250rwkw, again depending on the condition of the box..

if your going to abuse it, a built c4 will be needed at a cost of between $3000-5000..

I'm a build it once build it properly guy, and want it to last.

Is the AU engine the pick over EF or EL?

Is there a specific model of the C4 to go for or are they all the same? What is the bell housing I need?

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